Fibromyalgia syndrome (FMS) is an intractable disease of unknown cause, characterized by the symptoms such as chronic systemic pain, fatigue and sleep disorder. Morbidity of FMS is very high in women, and the estimated number of patients in Japan is about 2 millions (˜3% of the population are affected in USA according to the American Fibromyalgia Association). However, diagnosis of FMS is extremely difficult, and sometimes it takes 5 to 10 years for the patient to be suspected and finally diagnosed as FMS. FMS is fundamentally different from other intractable diseases because no anomaly is found in the clinical parameters currently used in many hospitals. As a result, FMS patients are often diagnosed as having mental disorders. Moreover, since many physicians do not regard FMS as a disease, FMS patients suffer from the disease physically and mentally. Aggravation of FMS can be prevented by an appropriate treatment at an early stage of pathogenesis. However, the symptom will aggravate if the patient fails to receive an appropriate treatment at early stage. Thereafter, FMS patients will suffer intolerable pain, fatigue and eventually have a difficulty even in daily life.
Sound diagnosis of FMS is more difficult due in part to the confusion with other diseases that exhibit similar symptoms. For example, systemic pain is not a symptom specific for FMS, but it also occurs in other diseases such as rheumatoid arthritis (RA) and spondyloarthritis (SpA). Further, FMS patients often suffer from SpA and/or RA simultaneously. Accordingly, differential diagnosis of FMS is difficult even for a specialist of RA or of the pain clinicians. A current method for diagnosing FMS is a tender point test. However, because it relies on the pain at the tender points, it is not objective, rather subjective in nature. Thus, there has been a demand for an advent of method(s) to differentiate FMS from other pain-provoking diseases promptly, accurately and objectively.
Regarding determination of FMS, some technics using a molecular marker or the like are known (see WO1997/014963, WO2012/046708, and WO2010/004962).